The present invention relates generally to fluid flow connections and, more particularly, to behind-the-wall plumbing constructions.
A wide variety of fittings and fixtures are available for connection to a fluid flow conduit or pipe in plumbing constructions. It is important that these constructions provide a reliable fluid tight seal, especially in behind-the-wall constructions where pipe-fitting connections are relatively inaccessible. It is also important these connections be made quickly and simply, especially in mobile home and modular housing constructions where production and component costs must be kept to a minimum.
In constructions where weight and cost have to be minimized, it has been suggested that various plastic fittings and pipes or combinations of metal and plastic fittings and pipes be employed. While these arrangements are typically acceptable in low pressure, exposed plumbing constructions, objections have been raised with respect to fire protection and behind-the-wall applications.
Many plumbing constructions using all plastic components fail to meet the high pressure rating standards required by the industry and government for use in behind-the-wall constructions. Plumbing constructions using metal/plastic combinations are typically mechanically joined and also fail to meet industry standards for behind-the-wall constructions. Those metal/plastic connections that do pass the ratings test are relatively expensive to produce. Some plastic component constructions are permissible for cold water and/or low pressure applications, but not for hot water and/or high pressure uses. Other plastic component constructions are acceptable only for non-portable or non-standing water systems. Thus, they are not suitable for residential plumbing and fire protection applications, respectively.
Polybutylene is a material which would be especially suitable for use in plumbing constructions. Polybutylene piping is sufficiently rigid and strong enough to pass even fire protection and behind-the-wall rating standards. Polybutylene may be quickly and inexpensively extruded into both tubing and pipe and molded into a wide variety of fittings and fixtures. This material also remains stable and retains its flexibility, shape and fluid flow integrity over a wide range of temperatures. Further, polybutylene is substantially chemically inert and, thus, is not subject to corrosion or deterioration in potable water application.
However, it has been extremely difficult to provide an adequate connection between polybutylene plumbing components, such as a pipe end and a T or L fitting. While polybutylene is chemically inert with respect to most corrosive materials, it is likewise inert with respect to adhesives. Polybutylene piping is usually also too soft to thread sufficiently to form a fluid-tight seal. Mechanical bonds, such as crimping a portion of polybutylene tubing to a fitting, are available, but often only at a prohibitive cost and requiring a restriction in the fluid-flow path. Also, crimping methods require significant amounts of working space and do not always produce reliable connections unless extreme care is taken in assembly. Heat fusion techniques, wherein individual components are heated and then pressed together, have not been altogether successful even where both components are polybutylene. Again, assembly techniques are critical and, on occasion, the polybutylene elements have been fused but without welding, and therefore have not remained fluid-tight up to the required pressure ratings. As a result, acceptable plumbing constructions formed entirely from polybutylene components have not achieved widespread commercial application.
It is therefore an object of the present invention to provide an improved plumbing construction.
Another object is the provision of an inexpensive and reliable tubular connection for fluid flow systems.
A further object is to provide a pipe-fitting connection formed entirely from polybutylene components.
Yet another object is the provision of a method of assembling polybutylene components into a fluid-tight construction suitable for behind-the-wall applications and an apparatus for friction welding a plurality of polybutylene elements simultaneously.
Still another object is to provide an inexpensive plastic-component plumbing construction suitable for use in fire protection applications.
These and other objects of the present invention are attained by the provision of a plumbing construction including a pipe, a fitting, and a bushing, each formed from polybutylene and providing a fluid-tight connection between the pipe and the fitting. The bushing is mounted about the pipe and an end of the pipe and the bushing is inserted into the fitting. The bushing is rotated with respect to the fitting to produce friction welds between the bushing and both the pipe and the fitting.
In preferred embodiments of the present invention, the bushing is telescopically mounted on the pipe and the pipe and bushing form interference fit, telescopic joints with respect to the fitting. The fitting is formed with internal steps which serve as abutments for the ends of the pipe and the bushing. The end of the bushing inserted within the fitting is tapered, and the external surface of the bushing includes projections to assist in engagement by a means for rotating the bushing while in an inteference fit with respect to the fitting.
A preferred method of assembling the pipe, bushing and fitting components would include initially inserting the bushing onto the pipe and then the pipe into the fitting and then securing the fitting against rotation. The bushing is next slid along the pipe into the fitting. The tool for rotating the bushing engages the exterior surface of the bushing and rotates it until the friction welds are sensed.
Other objects and advantages of the present invention will be apparent from the following detailed description of preferred embodiments when considered in conjunction with the accompanying drawings.